Fuel burner controls



Sept. 1965 P. w. THOMPSON 3,207,204

FUEL BURNER CONTROLS Filed Sept. 13, 1965 3 Sheets-Sheet l INVE NTOR Fq'ge H4 Thaw v50);

Sept. 21, 1965 P, w. THOMPSON 3,207,204

FUEL BURNER CONTROLS Filed Sept. 15, 1963 s Sheets-Sheet 2 70 INVENTOR.

Fvge W Thompson,

Ht't'ar'ny- P 1965 P. w. THOMPSON 3,207,204

FUEL BURNER CONTROLS Filed Sept. 13, 1963 3 Sheets-Sheet 3 INVENTOR. Page 14 Flam 05v,

BYZAAV mum,

United States Patent 3,207,204 FUEL BURNER CONTROLS Paige W. Thompson, Morrison, 11]., assignor to General Electric Company, a corporation of New York Filed Sept. 13, 1963, Ser. No. 308,897 6 Claims. (Cl. 158-428) This invention relates to fuel burner controls and more particularly to an improved control for automatically igniting and controlling the operation of a gas burner.

In the type of controls used for opera-ting fuel burners, for example, the master control used to operate the gas burner in a clothes dryer, space heater and other gastired equipment, it is necessary that some means be provided for shutting off the supply of gas in the event the burner flame is extinguished or if ignition of the gas fails to take place. Generally, in the event of such failures, the control will allow the gas or other fuel to be supplied to the burner tor a predetermined interval and if ignition does not occur within the interval, the control will cause the supply of the gas to be shut off to prevent dangerous accumulations of gas.

A commonly used control for a gas burner employing electric ignition, utilizes a safety lockout switch, which is operated with a delayed action by a lockout heater connected in parallel with a hold resistor. The safety lockout switch comes into play to cut off the power to the solenoid or coil of the gas valve, when the gas fuel is not within a permissible interval, initially ignited, or reignited after a flame failure. Such conventional controls do not usually cause the system to fail safe, i.e., shut off the power to gas valve solenoid and to the igniter, when the connections to the safety lockout heater or the lockout heater itself fails during the operating condition of the fuel burner. It is particularly desirable that a control for a fuel burner cause the system to completely fail safe when such failures occur.

Accordingly, a general object of the present invention is to provide a control for operating a fuel burner incorporating improved safety features.

A specific object of the invention is to provide a fuel burner control that will cause the system to fail safe in the event that the loclcout heater or connections thereto fail.

It is another object of the present invention to provide an improved fuel burner control that utilizes components that are relatively simple and inexpensive in construction and that insure safe operation of the burner;

In accordance with one form of my invention I have provided an improved control for use in conjunction with a fuel burner, a fuel control valve and an electrical igniter. The control includes a safety "lockout heater for actuating a lockout switch, a main relay coil for operating a normally open relay switch and a hold resistor for limiting the current to the relay coil to a value above its holding current value but below the value required to activate the safety lockout heater. The lockout heater, the relay coil and the hold resistor are connected in series circuit relationship in an operating circuit branch. The operating circuit branch is connected in circuit across the supply terminals or connections provided for energization from an alternating current source.

In order to detect the presence or absence of combustion, I have provided a combustion responsive means which actuates a first and a second normally closed combustion switch to an open condition when combustion is established. One of the combustion responsive switches is connected across the hold resistor to provide a shunt path so that the current to the relay coil and lockout heater will 'be at a level sufiicient to actuate the relay coil, and to activate the lockout heater if combustion 3,207,204 Patented Sept. 21, 1965 ice is not established after a predetermined time interval. The second combustion switch is connected in series circuit relation with the igniter. Further, the igniter and the second combustion switch are connected in series in a starting circuit branch connected across the supply terminals, and a gas valve control coil is connected in parallel circuit across the starting circuit branch. The lockout and relay switches are joined in series circuit between the operating circuit branch and the starting circuit branch and in circuit with one of the supply terminals so that when either of these switches are in the open position, the power to the igniter and the gas valve control coil is interrupted.

With the safety lockout heater connected in series circuit relation with the hold resistor and the main relay coil, the control causes the fuel burner system to fail safe in the event that the safety lockout heater or the connections thereto fail. Thi safety feature is accom- .plished without the need for additional components, such as switches and the like.

Further aspects of the invention will become apparent from the more detailed description of the invention which follows. It will be understood that the specification concludes with claims which particularly point out and distinctly claim the subject matter which I regard as my invention. The invention, however, both as to organization and method of operation, may be best understood with reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is a diagrammatical view of the improved control embodying one form of the invention particularly adapted for a gas burner application, the switches being shown in their normal position for the cold condition of the control;

FIGURE 2 is a simplified circuit diagram of the control illustrated in FIGURE 1 with the components of the control shown schematically and arranged to more clearly illustrate the relative circuit connection between the components;

FIGURE 3 is a diagrammatical view of the control corresponding to the view shown in FIGURE 1 and showing the relative positions of the switches when the control is in the hot or operating condition;

FIGURE 4 is a simplified circuit diagram of the control corresponding to FIGURE 3 with the componentsof the control shown schematically and arranged to moreclearly illustrate the relative circuit connections between the components;

FIGURE 5 is a plan view of the control with the cover plate removed to show the physical arrangement of the components; and i FIGURE 6 is a side elevational view of the control corresponding to the view shown in FIGURE 5.

Referring now in more detail to the drawings, I shall now more particularly describe the improved control 10 as applied to a gas burner 11 having associated therewith a solenoid operated valve 12 and an igniter 13. The gas burner 11 includes the adjustable air intake openings 14, a reflector 15, and an essentially tubular chamber 16 formed with a narrow throat section 17.

Gaseous fuel is admitted to the burner 11 by a gas inlet pipe 18 which projects into the gas burner 11 through an opening provided at the end thereof. A controlled supply of air is admitted to the burner 11 through the adjustable air intake openings 14. During operation of the burner 11, a mixture of the gaseous fuel and air is conducted through the chamber 16, which functions as a Venturi tube, and the mixture of air and fuel is ignited in the vicinity of the outlet by the igniter 13.

The supply of gaseous fuel is controlled by an electromagnetically operated gas valve 12 which is opened by energizing gas valve control coil 19. When the coil 19 is deenergized or when the current through the coil 19 falls below the holding value, the valve 12 returns to the closed position by gravity, a spring or other suitable bias means (not shown).

- In order to initiate combustion of the fuel, a pair of electrodes 20, 21 of the igniter 13 have their igniter tips 22, 23 disposed near the burner outlet in proper location with respect to the fuel stream. It will be seen that electrode 20 is fixed while the other electrode 21 is arranged for relative rotational movement with respect to the fixed electrode 20. The movable electrode 21 is driven by the armature 25 and oscillated at a relatively low frequency when the igniter coil 24 is energized. Further, it will be noted that the movable electrode 21 is biased by a spring 26 to a normally closed position. An electric arc is generated between the igniter tips 22, 23 as the movable electrode 21 is intermittently rotated out of engagement with the fixed electrode 20. The fixed or stationary electrode 20 is connected in electrical circuit with the coil 24 by means of a connection 27 and the movable electrode 21 is connected in electrical circuit with lead 28 through the contact 29 to join the electrodes 20, 21 in series circuit relation with the igniter coil 24. The spring force exerted by the spring 26, the inertia of the armature-electrode mass system, and the torque developed by the armature 25 are the factors that determine the frequency at which the igniter tips 22, 23 are opened and closed during the ignition period. A frequency of approximately cycles per second provides satisfactory ignition in the illustrated application.

The combustion responsive means used in the exemplification of the invention includes a flame detect-or tube 30 positioned in proximity to the burner 11, an operating arm 31 and a pair of combustion switches 32, 33. The presence of the gas flame near one side of the tube 30 results in a temperature differential between one side and the other, which causes the flame detector tube 30 and the operating arm 31 to deflect to the position shown in FIGURE 3. When so deflected, the operating arm 31 actuates the first combustion switch 32 and the second combustion switch 33 to the open position. It will be seen that an adjustable screw 34 carried by the operating arm 31 provides a means for adjusting the position of the arm 31 with respect to the push button 35.

Having more specific reference now to the combustion switches 32 and 33, I will now more fully describe these switches. The first combustion switch 32 includes a relatively fixed contact 36 and a movable contact 37 carried near the free end of a flexible strip 38 supported fixedly at the other end. A finger 39 extends downwardly from the free end of the flexible strip- 38 so as to engage the push button 40 of the second combustion switch 33 when the operation arm 31 is deflected. The second combustion switch 33 includes a relatively fixed contact 41 and a movable contact 42 carried on a flexible strip 43. The first combustion switch 32 is connected across the hold resistor 44 by leads 45, 46, 47, to short-circuit the hold resistor 44 when the switch 32 is closed. The second combustion switch 33 is connected in the second circuit branch containing the igniter 13 by leads 48 and 49 and opens the electrical circuit in the second circuit branch when switch 33 is actuated to the open position. Thus, when combustion is established, this switch causes the igniter 13 to be deenergized.

A lockout switch 50 operable by a lockout heater 51, interrupts the power to the gas valve coil 19 and igniter 13 under certain conditions as will hereinafter be more fully discussed. The lockout switch 50 includes a relatively fixed contact 52 and a deflectable switch arm 53 carrying a contact 54. In the illustrated exemplification of the invention, if combustion did not take place within less than 90 seconds after the control 10 was energized, the heat generated in the lockout heater 51 was sufiicient to deflect the switch arm 53 and open the lockout switch 50. It will be understood, as will hereinafter be more fully explained, that when the hold resistor 44 is not short-circuited, the current supplied to the lockout heater 51 is insufficient to actuate the lockout switch 50.

A main relay switch 55, which is normally in an open position when the control 10 is in the cold condition, is almost instantaneously closed when the control switch 65 is closed in response to a demand for combustion. The switch may be a thermostat, a timer or other switching means. The type of switch employed, will, of course, depend upon the particular application of the control 10. The relay switch 55 includes a relatively fixed contact 56 and a movable contact 57 carried near the free end of the flexible strip 58, a pivotally supported operating arm or armature 59, a push button 60, a relay coil 61, a core 62 and a support bracket 63. The operating arm 59 is normally biased by a spring 64 to hold the relay switch 55 in a normally open position when the relay coil 61 is not energized or when the current through the relay coil 61 falls below the holding current value of the relay switch. The relay coil 61 used in the exemplification of the invention had a pick-up value of .095 ampere and a holding current value of .035 ampere. As will hereinafter he more fully described in connection with the description of the operation of the circuit, an open circuit type of failure in the lockout heater 51, the relay coil 61 or the hold resistor 44 will cause the relay switch 55 to be deenergized and restored to its normally open position.

Supply terminals or connections 66, 67 are provided for energization from a suitable alternating current supply, such as a 120 volt, 60 cycle supply. In the exemplification of the invention terminal 67 was adapted for connection to the ungrounded or black lead of the power supply.

Having more specific reference now to the simplified schematic circuit diagrams of the control 10 as shown in FIGURES 2 and 4, I will now more fully describe the circuit connections of the components of the control 10. The lockout heater 51, the relay coil 61 and the hold resistor 44 are connected in series circuit relation with each other in the first or operating circuit branch which is connected across the supply terminals 66, 67. It will be noted that the first combustion responsive switch 32 is connected in a shunt across the hold resistor 44. Thus, when control switch 65 is initially closed to energize the control 10, the hold resistor 44 is short-circuited. The current through the operating circuit branch is essentially limited only by the impedance of the lockout heater 51 and the relay coil 61 and is suflicient to close the relay switch 55.

The igniter electrodes 20, 21, the igniter coil 24 and the second combustion responsive switch 33 are connected in series in the starting circuit branch of the control 10. It will be noted that the gas valve control coil 19 is connected across the starting circuit branch by leads 70, 71. The lockout switch 50 and the relay switch 55 are connected, preferably, in circuit with the terminal 67 between the operating and starting circuit branches, as shown, so that when either the lockout switch 50 or the relay switch is open, the supply of power is interrupted to the starting circuit branch and to the gas valve control coil 19.

In FIGURES 5 and 6, I have illustrated a plan and side view to show the physical arrangement of the components of the control 10 as employed in the illustrated embodiment of the invention. It will be appreciated that these Views are not intended to show the specific circuit connections. The control 10 is housed in a control box with the cover plate (not shown) and is supported on a U-shaped frame 75. It will be seen that the control or main relay 55 is attached to the U-shaped frame at the left end. The relay 55 includes the relay coil 61, the core 62 disposed within the coil 61, the armature or operating arm 59, the spring 64 and the bracket 63. The

operating arm 59 is pivotally carried on the bracket 63 by assembling the indented portion 76 of the arm 59 into a recess 77 formed in the bracket 63, as will be seen in the view illustrated in FIGURE 5. The spring 64 is attached at one end to a tab 78 extending from the bracket 63 and is attached at the other end to a tab 79 on the arm 59.

As shown in FIGURE 5, the hold resistor 44 is connected to a terminal of the relaycoil 61. At the right hand side of the U-shaped frame 75 a stack 80, on which switching elements of the control are supported, is attached to the frame 75.

It will be seen that the lockout heater 51 is wrapped around the flexible arm 53 and is supported thereon. The contacts 52, 54 of the lockout switch 50 are shown in the closed position. Further, it will be noted that relatively fixed arms 81, 82 supporting contacts 52, 56 of the lockout and relay switches 50, 55 are sandwiched together in the stack 80 to provide a good electrical connection therebetween.

As will be seen in the view shown in FIGURE 6, the relatively fixed contact 36 of the first combustion responsive switch 32 is carried on an angled support arm 83. The relatively fixed contact 42 carried on a similarly angled support arm 84 lies under the flexible strip 38 which carries the relatively movable contact 37 of the first combustion responsive switch 32. The support arm 84 carrying the contact 42 is located under the first combustion switch 32 so that when the operating arm 31 of the flame detector tube 30 isdeflected downwardly, as seen in FIGURE 6, the actuating screw 34 engages the push button 35 and effects a displacement of the free end of flexible strip 38 and finger 39 to thereby open the first and second combustion responsive switches 32, 33.

The flame detector tube 30 is supported in an aperture provided in the U-shaped frame 75 and extends outwardly of the frame 75 so that the tube can be properly positioned with respect to the burner 11. When the flame detector tube 30 is heated at one side so that a temperature differential exists between one side of the tube 30 and the other side, the tube 30 warps effecting a downward movement of the actuating screw 34. In this manner both of the combustion responsive switches 32, 33 are actuated from a normally closed to an open position.

Referring now more particularly to the diagrams shown in FIGURES 1-4, I will now more fully describe the operation of the improved control 10. In FIGURES 1 and 2 I have shown the position of switches 32, 33, 50, 55 and 65 for the cold condition of the control 10.

The control 10 is energized when switch 65 is closed in response to a demand for heat. Initially, current flows only in the operating circuit branch, and the path of current flow during an arbitrary half cycle of the alternating supply is through the supply connection 67, switch 65, combustion responsive switch 32, relay coil 61, lockout heater 51 and the supply connection 66. Since the hold resistor 44 is essentially short-circuited, the magnitude of the current in the operating circuit branch is now above the pickup value of the relay coil 61, and the relay switch 55 closes almost instantly when the control 10 is energized to supply power to the igniter 13 and the gas valve control coil 19.

Normally, under these conditions the gas fuel will be ignited. The presence of a flame in the vicinity of the flame detector tube 30 will cause a deflection of the tube 30, and the combustion switches 32, 33 will be actuated to the open position as shown in FIGURES 3 and 4. When this occurs, the power supplied to the igniter 13 is interrupted to turn off the ignition, and the shunt path across the hold resistor 44 is opened. The hold resistor 44 is now effective in the operating circuit branch to limit the level of the current flowing therein so that it is above the holding value of the relay coil 61. In the illustrated exemplification of the invention the ohmic value of the hold resistor 44 was 2200 ohms. When 6 the hold resistor 44 is not short-circuited by switch 32, the power supplied to the lockout heater 51 is not sufi'icient to activate the flexible strip 53 of the lockout switch 50.

When switch 65 is opened in response to a demand for a cessation of heating, the relay switch 55 immediately opens to interrupt the supply of power to the gas valve control coil 19 thereby stopping the supply of gas fuel to burner 11. The absence of flame is detected by the flame detector tube 30, and after a pretermined interval (approximately 6 seconds in the illustrated embodiment) the combustion switches 32, 33 are restored to a closed position. The control 10 is now ready to reply to a demand for heat if required to do so.

If, when the control 10 is energized in response to a demand for heat, combustion of the gas is not successfully established within the interval-in which the lockout heater 51 is heated to a point where it causes the lockout switch to open, the supply of gas and ignition is turned off. In the exemplification of the invention this interval was approximately between 10 and 90 seconds for maximum and minimum supply voltages. The lockout switch will remain in the open position until the operating circuit branch of the circuit is deenergized by opening the control switch 65. It will be appreciated that when the lockout switch 50 is open and relay switch is closed, the supply of power to both the gas control valve coil 19 and the igniter 13 is interrupted. Since the first combustion switch 32 is closed during this condition of the control 10, the holding resistor 44 is bypassed and the current in the operating circuit branch is above the pick-up value of the relay coil. Consequently, the relay switch 55 is closed during this condition of the control 10.

When the control 10 is in the running or operating con dition, as shown in FIGURES 3 and 4, and a flame failure occurs, the temperature across the sides of the flame detector tube 30 will equalize and the operating arm 31 will return to its cold position to reset the combustion switches 32, 33 to their closed position. With these switches closed, the igniter 13 is energized to provide ignition and the hold resistor 44 is short-circuited. If combustion is established within the permissible interval (the time required to heat the lockout heater 51 to the point'where the lockout switch 50 will open), the control 10 will restore the burner 11 to its running condition. However, if combustion is not established within this interval, the lockout switch 50 opens to deenergize the gas valve control coil 19 and the igniter 13. The control 10 will remain in the lockout condition until the control switch is opened.

Let us assume that the control 10 is in the runing condition as shown in FIGURES 3 and 4 and an open circuit type of failure occurs in the lockout heater 51. An open circuit in the lockout heater 51 results in an interruption in the current supplied to the operating circuit branch of the control 10. Thus, the current to the relay coil 61 is interrupted, and the relay switch 55 is opened. With the relay switch 55 in the open position, power to the igniter 13 and gas valve control coil 19 is cut off. Consequently, the burner 11 fails safe.

A similar condition results if a connection to the relay coil 61 or the coil 61 itself fails during the running condition of the control. Also, an open circuit failure of the hold resistor 44 during the running condition will cause the relay coil 61 to be deenergized and open the relay switch 55. If the failure of the hold resistor 44 occurs when the control is in the cold condition, the control 10 when energized will cause combustion to be established. However, when the combustion switch 32 opens, the operating circuit branch is not open-circuitcd and the relay switch 55 opens. This will shut the gas off, but upon resetting and closing of switch 32, the device will reignite. Upon detection of flame switch 32 again opens and causes relay coil 61 to be deenergized. This condition may be repeated several times until the lockout resistor 51 opens switch 50. Thus,-the control 10 causes the burner 11 to fail safe.

If an open circuit type of failure occurs in the igniter coil 24 during the running condition, this will have no immediate effect on the operation of the burner 11 until operation is stopped in response to a demand for a cessation of heating and the switch 65 is again closed in response to a demand for heat. With an open-circuited igniter coil 24, ignition is not provided, and the combustion switches 32, 33 remain closed. The lockout heater 31 comes into play and opens the lockout switch 50 to cause the fuel burner 11 to fail safe.

An open circuit type failure of the gas valve control coil 19 during the running condition will cause the gas valve 12 to close. The flame detector tube 30 quickly detects the absence of the flame and closes the combustion switches 32, 33. Since the hold resistor 44 is now short-circuited, the lockout heater 51 takes over and actuates the lockout switch 50 to the open position thereby causing the burner 11 to fail safe.

From the foregoing description of the control and its operation, it will be apparent that I have provided an improved arrangement for safely controlling the operation of a fuel burner. An important advantage of the improved arrangement is that if the safety lockout heater, the main relay coil, or their connections fail, the control will cause the burner to fail safe.

Although the present invention has been described by reference to a particular embodiment thereof, it is to be understood that many modifications may be made to the improved control arrangement by those skilled in the art without actually departing from the invention. For example, it will be apparent that other suitable forms of combustion responsive devices may be used to detect the presence or absence of combustion. Also, it will be apparent to those skilled in the art that the relay coil, the safety lockout heater and the holder resistor can be rearranged in the-circuit without basically changing the functional arrangement. It is, therefore, intended by the appended claims to cover all such modifications that fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a control for use with a gas burner, a gas valve including a control coil and an igniter including an igniter coil, a lockout heater and a lockout switch operable by said lockout heater when the current through the lockout heater is at a first predetermined level for a selected interval, a relay coil and a relay switch operable by the relay coil for closing the relay switch when the current through the relay is at the first predetermined level, said relay coil being connected in series circuit relation with said lockout heater, a current limiting means connected in series circuit relation with said serially connected relay coil and lockout heater to limit the current to a second predetermined level below the value required to actuate the relay switch and at .a value sufficient to hold the relay switch closed but insufficient to heat the lockout heater to actuate the lockout switch, a pair of supply terminals for connection to an alternating current supply, circuit means connecting said serially connected lockout heater, relay coil and current limiting means in a circuit branch across said supply terminals without any circuit connection in parallel with said lockout heater in the circuit branch connecting said relay coil across said supply terminals, at least one combustion responsive switch, said combustion responsive switch being connected in shunt with said cunrent limiting means to cause current to be provided to said relay coil and lockout heater at said first predetermined level when said switch is closed and at the second predetermined level when opened, said combustion responsive switch being actuated when combustion is initiated, and circuit means for connecting the igniter in parallel with the gas valve control coil across the supply terminals, said lockout and [relay switches being joined in a series circuit with one of the supply terminals, the gas control valve coil, and the igniter to thereby cause the gas control valve coil and igniter to be deenergized when either said lockout switch or said relay switch is opened.

2. In a control for use in conjunction with a gas burner; an igniter, a gas valve including a control coil, a lockout switch, a lockout heater coupled with the lockout switch to actuate said lockout switch with a delayed action, a relay switch, a relay coil coupled with the relay switch to actuate said relay switch, said relay coil connected in series circuit with said lockout heater, a hold resistor connected in series circuit with the serially connected relay coil and lockout heater to limit the current to the relay coil to at least the holding current value of the relay coil, a pair of supply connections for energization from an alternating current supply, a first circuit branch connected across said supply connections and including said lockout heater, relay coil and hold resistor, a combustion responsive switching means including at least one switch, said switch being connected in shunt with said hold resistor, and being actuated t0 the open position in response to the initiation of combustion, a second circuit branch connected in circuit across the supply connections and including the igniter coil, means connecting the gas valve coil in parallel with said second circuit branch, said lockout switch and said relay switch joined in series with one of said supply connections and said parallel connected second circuit branch and gas valve coil circuit to interrupt the power to said second branch and the gas valve coil when either of said lockout and relay switches is open, whereby an open-circuit type of failure in said lockout heater causes said fuel burner to fail safe.

3. In a control for use in conjunction with a fuel burner; a fuel valve including fuel valve control means, a pair of supply connections from an alternating current supply, a normally closed lockout switch, a lockout heater coupled with the lockout switch to open the lockout switch when the current through said lockout switch remains above a predetermined level for a selected interval, a normally open relay switch, a relay coil for nected in series circuit relation with said lockout heater operating said relay switch, said relay coil being conand closing the relay switch when energized with current at said predetermined level, .a hold resistor connected in series with said serially connected relay coil and lockout heater and limiting the current thereto to at least the holding current level of the relay coil, a first circuit means connecting said relay coil, said lockout heater and said hold resistor across the supply connections, a combustion responsive switching means having a switch connected in parallel with the hold resistor and, a second circuit means connecting the fuel valve control means across the supply connections, said lockout switch and relay switch being connected in said second circuit means to thereby cause said gas valve to be deenergized when either said lockout or said relay switch is in the open position, whereby an open-circuit type of failure in the lockout heater or the relay coil causes said control to fail safe.

4. In a control for use with a gas burner; a gas control valve including a control coil and an igniter, a lockout heater and a lockout switch being operable by said lockout heater when the current through the lockout heater is held at a first predetermined level for a selected interval, a relay coil and a relay switch operable by the relay coil for closing the relay switch when the current through the relay is at the first predetermined level, said relay switch being in a normally open position and said lockout switch being in a normally closed position, said relay coil and said lockout heater being connected in series circuit relation, a current limiting means connected in series circuit with said serially connected relay coil and lockout heater to limit the current thereto to a second predetermined level sufiicient to hold the relay switch in a closed position, a pair of supply connections from an alternating current supply, circuit means connecting said serially connected lockout heater, relay coil and current limiting means in a circuit branch across said supply connections without any circuit connection in parallel with said lockout heater in the circuit branch connecting said relay coil across said supply connections, a combustion responsive switching means including a first and second combustion switch, said combustion switches being actuated in response to the presence of combustion, said first combustion switch being connected in bypass relation with said current limiting means to cause current to be provided to said serially connected relay coil and lockout heater at the first predetermined level when in the closed position and at the second predetermined level when in the open position, and circuit means for connecting the igniter in series with said second combustion switch and connecting said serially connected igniter and second combustion switch in parallel with the gas valve control coil across the supply connections, said lockout and relay switches being joined in series circuit with one of said supply connections and said gas valve control coil to thereby cause at least the gas control valve to be deenergized when either said lockout switch or said relay switch is open.

5. In a control for use with a gas burner, a gas valve including a control coil and an igniter, a pair of supply terminals for energization from an alternating current supply, a first circuit branch connected in circuit across the supply terminals, a second circuit branch connected in circuit across the supply terminals and in parallel with said first circuit branch, means for joining the gas valve control coil in parallel circuit relation across the second circuit branch, a lockout switch and a lockout heater, said lockout heater connected in said first circuit branch to open the lockout switch if ignition fails or does not occur, a relay switch and a relay coil, said relay coil connected in series with said lockout heater in said first circuit branch, a hold resistor connected in series with said serially connected lockout heater and relay coil, said hold resistor limiting the current to said serially connected lockout heater and relay coil to a predetermined level, a combustion responsive switching means including at least one combustion switch, said combustion switch being connected across said hold resistor to cause current to be provided to said serially connected relay coil and said lockout heater at another predetermined level when the combustion switch is closed, means connecting the igniter in said second circuit branch, said lockout switch and said relay switch in series circuit with one of said supply terminals and said second circuit branches to thereby interrupt the power to the igniter and gas control valve coil when either said lockout switch or said relay switch is actuated to the open position,

whereby an open circuit type of failure of said lockout heater or said relay coil causes the gas burner to fail safe.

6. In a control for use with a fuel burner, an igniter means and a fuel valve for controlling the supply of fuel to the fuel burner, a fuel valve control coil for opening and closing said fuel valve, said fuel valve being opened by energizing said fuel valve control coil and closed by deenergizing the coil, and said igniter means having electrodes and an igniter coil, said igniter coil when energized causing an electrode to be actuated to provide an electric are for ignition, a pair of supply terminals for connection to an alternating current supply, an operating circuit branch connected in circuit across the supply terminals, a starting circuit branch connected in circuit across the supply terminals and in parallel with said operating circuit branch, a normally closed lockout switch, a lockout heater connected in said operating circuit branch to open said lockout switch in a predetermined interval if ignition fails or does not occur, a normally closed relay switch, a relay coil connected in series with said lockout heater in said operating circuit branch for closing the relay switch, a hold resistor connected in said operating circuit branch in series with said lockout heater and relay coil to limit the current to the relay coil to a level suflicient to hold the relay switch in a closed position but insufficient to cause the lockout heater to actuate the lockout switches, a combustion responsive switching means having a first normally closed switch connected in shunt with the hold resistor for short-circuiting the hold resistor during the ignition period and a second normally closed switch for energizing the igniter during the ignition period, said first and second switches being actuated to the open position in response to the initiation of combustion, said second switch being connected in series circuit relation with said igniter in said starting circuit branch, circuit means for connecting the fuel valve control coil across said starting circuit branch and including connections placing said lockout switch and relay switch in series circuit between said operating and starting branches and in circuit with one of said supply terminals, whereby an open-circuit type of failure in said lockout heater causes said fuel burner to fail safe.

References Cited by the Examiner UNITED STATES PATENTS 2,761,625 9/56 Dymski 158-28 X 2,772,727 12/56 Schell 15828 2,887,152 5/59 Wilder 158-28 3,086,583 4/63 Reichow 158-125 3,096,811 7/63 Gustafson 158128 X FREDERICK L. MATTESON, IR., Primary Examiner.

MEYER PERLIN, JAMES W. WESTHAVER,

Examiners. 

1. IN A CONTROL FOR USE WITH A GAS BURNER, A GAS VALVE INCLUDING A CONTROL COIL AND AN IGNITER INCLUDING AN IGNITER COIL, A LOCKOUT HEATER AND A LOCKOUT SWITCH OPERABLE BY SAID LOCKOUT HEATER WHEN THE CURRENT THROUGH THE LOCKOUT HEATER IS AT A FIRST PREDETERMINED LEVEL FOR A SELECTED INTERVAL, A RELAY COIL AND A RELAY SWITCH OPERABLE BY THE RELAY COIL FOR CLOSING THE RELAY SWITCH WHEN THE CURRENT THROUGH THE RELAY IS AT THE FIRST PREDETERMINED LEVE, SAID RELAY COIL BEING CONNECTED IN SERIES CIRCUIT RELATION WITH SAID LOCKOUT HEATER, A CURRENT LIMITING MEANS CONNECTED IN SERIES CIRCUIT RELATION WITH SAID SERIALLY CONNECTED RELAY COIL AND LOCKOUT HEATER TO LIMIT THE CURRENT TO A SECOND PREDETERMINED LEVEL BELOW THE VALUE REQUIRED TO ACTUATE THE RELAY SWITHC AND AT A VALUE SUFFICIENT TO HOLD THE RELAY SWITCH CLOSED BUT INSUFFICIENT TO HEAT THE LOCKOUT HEATER TO ACTUATE THE LOCKOUT SWITCH, A PAIR OF SUPPLY TERMINALS FOR CONNECTION TO AN ALTERNATING CURRENT SUPPLY, CIRCUIT MEANS CONNECTING SAID SERIALLY CONNECTED LOCKOUT HEATER, RELAY COIL AND CURRENT LIMITING MEANS IN A CIRCUIT BRANCH ACROSS SAID SUPPLY TERMINALS WITHOUT ANY CIRCUIT CONNEC- 